Fire detecting unit



1955 c. w. MITCHELL ET AL 2,714,643

FIRE DETECTING UNIT Filed Dec. 27, 1952 FlG.l FlG.2

l6 llllll'l NW; 14 49 Q 3:9 1 3a Charles W. Mitchell Samuel $.Aidlin INVENTORS ATTORfiEY United States Patent ()ffice 2,714,543 Patented Aug. 2, 1955 FIRE DETECTING UNIT Charles W. Mitchell and Samuel S.

New York, N. Y.

Application December 27, 1952', Serial No. 328,188 6 Claims. (Cl. 200-138) Aidli n,

acter described which constitutes a substantial improvement and advance over units of the same heretofore in use.

It is one object of the present invention to provide a fire detecting unit of the character described which, though thermostatically controlled, has its detecting and signalling circuit mechanically closed, to thereby provide more positive, more rapid and more certain operation of the unit.

t is also an object of the a fire detecting unit of the general type present invention to provide character described in which the detecting circuit is automatically broken and reset after the fire setting it off is abated and, therefore, eliminates any need for manual adjustment or resetting after each operation.

It is another object of the present invention to provide a fire detecting unit of the character described which is compact and of minimum bulk and may be easily and conveniently installed without interference with the free and unencumbered utilization of the space in which it is installed.

It is still another object of the present invention to provide an automatic fire detecting unit of the character described in which the operative or movable parts are wholly enclosed and protected to a maximum degree from the atmosphere and from the corroding and contaminating substances carriedby it, to insure long, efiicient, unhindered and unobstructed operation of the unit.

It is a further object of the present invention to provide an automatic fire detecing unit of the character described in which the operative mechanism is protected from physical contact with any objects that might be moved past or against the unit and from any damage that might result from such contact.

it is a still further object of the present invention to provide an automatic fire detecting unit of the character described which is of neat, attractive and decorative appearance and will in now way detract from the appearance of the surroundings among which it might be located.

It is yet a further object of the present invention to provide an automatic fire detecting unit of the character described which is composed of few and simple parts that are easy to manufacture and easy and convenient to assemble and which is, therefore, economical to prodime and to use.

The foregoing and other advantages and superiorities of the automatic fire detecing unit of the present invention will become more readily apparent to those skilled in the art from the embodiment thereof shown in the accompanying drawing and from the description following. It is to be understood, however, that such embodiment is shown by way of illustration only, to make the principles and practice of the invention more readily comprehensible, and without any intent of limiting the invention to the specific details therein shown.

In the drawings:

Fig. 1 is a plan view of the ment of a fire detecting unit of Fig. 2 is a plan view of the same;

Fig. 3 is a section taken on line 33 of Fig. 2; and

Fig. 4 is a more or less diagrammatic view showing the electric circuit through the unit.

Referring more specifically to the accompanying drawing, the fire detecting unit comprises a base or body, 10, which is formed of non-conducting material such as ceramic or plastic material, and may be of circular shape, as shown, and which may be provided with openings, 11, to receive screws by which it may be secured in place.

The body 10 may have a generally flat underside, 12, and its outer face may preferably have a bevelled or rounded edge, 14. The outer face may also have formed thereon a plurality, such as four (4) ribs, 15, which may preferably be radially disposed and may each terminate short of the center of the body 14), with inner faces perpendicular to the body It to form a well, 16, which, in the illustrative embodiments is shown as of rectangular shape. The outer face of the body it) may have a groove, 17, formed therein peripherally of the inner end of the well 16.

The ribs 15 may preferably be of ornamental, such as curved, shape or outline, as shown, to constitute, additionally, decorative elements for the unit and to enhance its appearance and decorative values.

A hollow plug, 2t likewise of non-conductive material and of an outer shape corresponding to the shape of the Well 16, is fitted into the well 16. The passageway, 22, through the plug 2% may be rectangular at the inner end of the plug to enable such inner end to fit into the groove 16, and it may taper outwardly to a circular opening, 23, in the outer end of the plug. The plug 20 may preferably be of a height that when its inner end is fitted into the groove 16, its outer end will be disposed inwardly of the highest points, 2 3, of the ribs 15, which thus form shields for the plug.

The thermostatic fire detecting mechanism is disposed in the outer portion of the plug passageway 22 and may comprise a cup shaped non-conductive, as plastic housing, 25, having the bottom wall, 26, and the opening, 27, and having an L-shaped metallic rim, 28, fitting about the edge of the opening with one leg thereof engaging the side of the housing 25 and the other leg extending over the edge of the opening 27 and partly over the opening itself, to flange, 29, therefor.

A pair of preferably L-shaped terminal elements or bars, 31, are disposed within the housing 25 in diametri cally opposed relation to one another, each having one leg extending outwardly of the bottom of the housing 25, through an opening or slot, 32, formed in the bottom wall 26 thereof, and having its other leg, 33, laterally inwardly offset, in facing relation to the other, leaving a gap between the two.

Each terminal 31 is connected elec.rically, either integrally or by rivet or soldering, to a conductor strip, 34, one end of which is disposed against the outer face of the bottom housing wall 26. Each strip 34 extends through a slot, 35, formed in the body 16', to the exterior thereof, where it is offset laterally and disposed in a groove underside of one embodithe present invention; outer side or face of the or recess, 36, formed in the underside of the body 21%,

3 and is held in place by a set screw, 37, which passes through an opening, 33, formed in the offset strip end and engages in the tapped opening, 39, provided in the body It the strips 34 thus serve also as anchoring means for the housing 25.

A floating bridge is provided to bridging the gap between the terminal ends 33 to close the electric circuit through the detector unit. This bridge may consist of a bar, 40, having a bead, ill, formed at each end of one of its faces. The bar 40 is maintained in normally floating position with each. bead ll over and inwardly of one of the terminal ends 33, by means of a triangular element or support, 42, the base of which supports the center of the bar 4%, on the side facing the opening 27 of the housing 25, and the apex of which rests on the center of a bi-metallic, heat-sensitive disc, 44, which is concave at normal temperatures and is disposed in the opening 27 of the housing 25 with its convex surface interiorly disposed and its edges supported on the flange 29 of the rim 28; the disc 44 thus also serving as a closure and seal for the housing 25. The height of the element 42 or its altitude is such that the distance between the beads 41 and the terminal ends 33, under normal temperature condition, is less than the height of the curvature of the disc 44- under normal temperature conditions, so that when the disc is flattened under the effect of rising temperature the bridge 4 may be brought to rest on the terminals 33 under the pressure of the curved leaf spring, 45, the arc portion of which rests on the inner surface of the bar 4% and the offset ends of which abut the inner face of the bottom wall 26 of the housing 25.

It will be apparent that under normal temperature conditions the bridge bar it) is maintained out of contact with the terminals 33, to form a gap in the electric circuit through the unit, and that when, in response to increased temperature, the disc 44 flattens, the bridge is pushed by the spring 45 to rest on the terminals 33 to close the gap in the circuit through the unit.

Binding posts may be provided at each end of the circuit through the unit by which the unit may be connected in parallel into an alarm signalling system. Each binding post, 4-7, may be T-shaped and may have the end, 48, of its leg portion laterally offset, and provided with an opening, 49, so that it may be placed over the end of the connecting strip 34 on the reverse side of the body it), and may be secured in place as well as in electrical contact with the strip by means of the screw 37. The cross bar, 50, of each binding post 47 may likewise be offset in the opposite direction and may be provided with terminals,

51, for connecting into an electrical circuit at each end thereof.

This completes the description of the fire detecting unit of the present invention. it will be apparent that such unit is decorative and is of minimum bulk, that its operative mechanism is relatively compact and is enclosed for maximum protection against the corroding elements of the atmosphere as well as against admission of foreign elements that might clog the mechanism and block its operation, and that, further, the operative mechanism of the device is also shielded against damaging physical contact with objects that may move past it.

It will be further apparent that numerous variations and modifications in the fire detecting unit of the present invention may be made by any one skilled in the art, in accordance with the principles of the invention hereinabove set forth and without the use of any inventive ingenuity. We desire, therefore, to be protected for any and all such variations and modifications that may be made within the spirit of the invention and the scope of the claims hereto appended.

What we claim is:

l. A fire detecting unit of the character described, comprising a base having an inner and outer face said base having on its outer face portions thickening toward a central part thereof and terminating short of one another, forming a recess between them, a plug having a longitudinal passageway formed therethrough set into said recess with its outer end terminating inwardly of the highest point of said thickened portions, and a heat responsive switch for closing an electrical circuit set into the outer opening of said passageway, said switch including a pair of spaced terminal elements each electrically connected to a conductor element passing through said plug and through openings formed in said base to the inner face of said base, and means securing said conductor elements to the inner face of said base to thereby secure said switch to said base and forming a terminal for the circuit through said switch.

2. A fire detecting unit of the character described comprising a base having an inner face and an outer face, said base member having radially disposed ribs formed on its said outer face, said ribs thickening in the direction of the center of the base and terminating short of one another to form a recess between them at approximately the center of the base, a plug having a longitudinal passageway formed therethrough set into said recess, and a heat responsive switch for closing an electric circuit through the unit set into said passageway in the outer opening thereof, the outer end of said plug and said switch mechanism disposed inwardly of the highermost point of said ribs, said switch including spaced terminals each connected electrically to a conductor element extending through said passageway and through opening formed in said base to the exterior of said base on the inner face thereof and means adapted to secure a binding post to said base securing said conductor elements to said base.

3. A fire detecting unit of the character described comprising a heat responsive switch for an electric circuit including a substantially cup-shaped, non-conducting housing, an L-shaped annular rim secured around the opening of said housing with one leg engaging the side wall of said housing and the other overlying the edge of the opening thereof and a portion of said opening, a. bimetallic heat responsive element disposed in said housing opening with its edges supported on said other rim leg, a pair of terminal members within said housing, a bridge for the space between said terminal elements and means for supporting and urging said bridge on and toward said bimetallic element, a base member having an inner face and an outer face, said base member having on its outer face portions thickening in the direction of a central point thereof and terminating short of said central point and forming a recess between their inner ends, a plug having a longitudinally disposed recess therein disposed within said base recess with the opening thereof outwardly facing, said housing seated into said plug recess with its rim overhanging the edges thereof, a conductor element connected to each of said terminal elements, said conductor elements each passing through said plug and through said base to the inner face thereof, and means securing said conductor element to the inner face of the base and thereby securing said plug and said switch to said base.

4. The unit of claim 3, wherein said thickening portions comprise radially disposed ribs thickening generally in the direction of the center of the base and terminating short of the center thereof, each having its inner face perpendicular to the base.

5. The unit of claim 3, wherein said means for securing said conductor elements to said base comprise an opening formed in the end of said conductor element, a registering opening formed in said base and a screw passing through said conductor element opening and set into said base opening.

6. The unit of claim 3, including a terminal post secured to said base in electrical contact with each of said conductor elements, said terminal posts secured in place by the means securing said conductor elements to said base, said last means including an opening formed in 5 each of said terminal posts and each of said conductor References Cited in the file of this patent elements, a tapped opening formed in said base in register UNITED STATES PATENTS with the opening in each of said conductor elements, and

a screw passed through the opening of a terminal post 1733085 Thomas 1929 and a conductor element and set into a tapped opening of 5 2230770 Van Almelo 1941 2,238,881 Evans Apr. 22, 1941 the base.

2,622,169 Cataldo et a1 Dec. 16, 1952 

